Alternative Procedures for Evaluation of Soybean Seed Vigor.

Speed and uniformity of seedling emergence and stand establishment are crucial issues to support high productivity soybean crops. As a consequence, the development and improvement of reproducible procedures to evaluate the physiological attributes of seed quality is a continuing need of seed industry. Soybean seed vigor has been primarily evaluated by the accelerated aging, electrical conductivity, tetrazolium and seedling growth tests, but there are still opportunities to improve methodology. The objective of this study is to verify the accuracy of some alternative procedures to detect differences in performance among soybean seed lots in comparison to the information from accepted vigor tests and seedling emergence results. Five seed lots each of two cultivars (Pintado and TMG 113RR) were subjected to standard germination, traditional accelerated aging (41^oC and 100% R.H. for 48h followed by germination at 25^oC for 4 days), saturated salt accelerated aging - SSAA (41^oC and 75% R.H. for 72h), electrical conductivity (subsamples of 25 seeds/75 ml water/25^oC/8h and 24h) and field seedling emergence. The following alternative procedures were studied: a) determination of Seed Vigor Imaging System (SVIS^®) parameters including mean seedling growth, uniformity and vigor index in images of 3-days old seedlings; b) SSAA followed by determination of SVIS^® parameters, and c) SSAA followed by evaluation of seed viability by terazolium test (seed conditioning at 40^oC for 6h and staining in contact with a 0.075% tetrazolium chloride solution at 40^oC for 2h). The experimental period comprised three evaluation times with 30-day intervals. Presentation of results will focus on comparisons of these alternatives with the recognized vigor tests and the estimation of seedling emergence from the perspective of accuracy, objectiveness, reducing testing time, reproducibility and reliability of results. The potential use of the procedures evaluated to assess soybean seed vigor and to compose seed quality control programs will be discussed.